Communication networks providing for bi-directional communication are well-known. An example of such a network, embodied in a CATV communication system, is provided in commonly assigned co-pending U.S. patent application Ser. No. 06/373,765, filed Apr. 30, 1982, now U.S. Pat. No. 4,533,948 entitled "CATV Communication System", and incorporated herein by reference (hereinafter, "the co-pending application").
The pending application referred to discloses a communication network built around frequency agile modems accessing multiple medium speed (128 kbp/s) channel pairs which are frequency division multiplexed into the available RF spectrum. Each channel pair comprises an upstream communication channel and a downstream communication channel. Each channel can carry a plurality of different signals through well known channel sharing techniques, such as that known as "CSMA/CD" and described in the copending application. This approach, as contrasted with the high speed (10 Mbp/s) baseband approach which is inherently distance limited, is not only compatible with standard CATV systems but has the geographic reach to cover even the largest CATV trunk runs (up to 30 miles).
Various applications are envisioned for such communication networks. Such applications include consumer or commercial services such as home banking, electronic mail and newspapers, shop at home, and the like. A provider of such services can couple its computers to the communication network so that the services can be accessed by a subscriber using an appropriate terminal ("subscriber terminal") coupled to the network. In providing such services, it is essential that security be provided. For example, a home banking customer must be able to accomplish transactions without divulging his personal identification number or other password to an intruder who may be monitoring the communication network.
A subscriber terminal may take several different forms, ranging from one with no intelligence to a "smart terminal" with the ability to complete various tasks locally. Smart terminals are desirable because they can relieve the communication network and its associated controllers from tasks which do not relate strictly to the provision of communication services. The operating system, communications protocol software, display package, and user interface software for the smart terminal can be provided on a disk or other storage medium used with the terminal, can be fixed in read only memory (ROM) installed in the terminal, or downloaded into random access memory (RAM) each time the terminal is powered up. The latter approach is advantageous in that system software can be modified, and each new release distributed via one of the channels of the communication network to each subscriber terminal. This approach enables a system operator to upgrade the software in literally hundreds of thousands of terminals merely by providing new software to be downloaded via the communication network. Thus, terminal products can evolve in place, rather than being made obsolete by changing market demands. An additional benefit of this approach is the ability to page individual software modules off of network channels on demand, reconfiguring subscriber terminals to optimally support a wide variety of diverse applications depending on what a given subscriber desires to do at a particular moment.
A potential problem may arise, however, with the downloading of software into subscriber terminals. In particular, a system intruder could download fraudulent software into a subscriber terminal, which data would be used to take control of the terminal without knowledge by the system operator or the subscriber. The intruder could then access a subscriber's bank account, shop at home account, or conduct other transactions and thereby steal funds, goods, and services.
It would be advantageous to provide a communication network which enables software to be downloaded into subscriber terminals without opening the network to intrusion by an unscrupulous third party. The present invention relates to apparatus and a method for providing such a communication network.